Abstract-The switching frequency of medium-voltage high power converters is limited to about 1 kHz due to semiconductor junction temperature constraint. The frequency band between the fundamental and carrier frequency is limited to a little more than one decade and the LCL filter design is usually a challenge to meet grid codes for grid connected applications. Traditional designs focus on the optimization of the filter parameters and different damping circuits. However, this design is very influenced by the modulation technique and produced low order harmonics. Widely used pulse width modulations (PWM), such as phase disposition PWM (PDPWM), produce low order harmonics that constraint the design of the filter. Selective harmonic elimination PWM (SHEPWM) can eliminate theses low order harmonics, enabling a more efficient design of the LCL filter. In this paper, the LCL grid filter of a Multi-Megawatt Medium-Voltage neutral point clamped (NPC) converter for a wind turbine is redesigned using SHEPWM modulation. Experimental results demonstrate that the efficiency of the converter, filter and overall efficiency are increased compared to that obtained with PDPWM.Index Terms-LCL filter, medium-voltage converter, selective harmonic elimination, SHE.
It is getting more common every day to install inverters that offer several grid support services in parallel. As these services are provided, a simultaneous need arises to know the combined limit of the inverter for those services. In the present paper, operational limits are addressed based on a utility scale for a real inverter scenario with an energy storage system (ESS) (1.5 MW). The paper begins by explaining how active and reactive power limits are calculated, illustrating the PQ maps depending on the converter rated current and voltage. Then, the effect of the negative sequence injection, the phase shift of compensated harmonics and the transformer de-rating are introduced step-by-step. Finally, inverter limits for active filter applications are summarized, to finally estimate active and reactive power limits along with the harmonic current injection for some example cases. The results show that while the phase shift of the injected negative sequence has a significant effect in the available inverter current, this is not the case for the phase shift of injected harmonics. However, the amplitude of the injected negative sequence and harmonics will directly impact the power capabilities of the inverter and therefore, depending on the grid-side voltage, it might be interesting to design an output transformer with a different de-rating factor to increase the power capabilities.
In this paper, a Frequency-Dependent Pi Model (FDPi) of a three-core submarine cable is presented. The model is intended to be used for the representation of submarine cables in an Offshore Wind Power Plant (OWPP) scenario for both time and frequency domain analysis. The frequency-dependent variation of each conductive layer is modeled by a Foster equivalent network whose parameters are tuned by means of Vector Fitting (VF) algorithm. The complete formulation for the parameterization of the model is presented in detail, which allows an easy reproduction of the presented model. The validation of the model is performed via a comparison with a well-established reference model, the Universal Line Model (ULM) from PSCAD/EMTDC software. Two cable system case studies are presented. The first case study shows the response of the FDPi Model for a three-core submarine cable. On the other hand, the second case study depicts the response of three single-core underground cables laying in trefoil formation. This last case shows the applicability of the FDPi Model to other types of cable systems and indirectly validates the response of the aforementioned model with experimental results. Additionally, potential applications of the FDPi model are presented.
In this paper, a detailed spectral analysis of an offshore wind farm, based on AC submarine cables is carried out. It is well known that due to the capacitive character of the AC submarine cables, it is very common to find resonance problems in the transmitted power, associated to this issue. For that reason, this paper first analyzes which is the proper "π" electric equivalent circuit to model the AC submarine cable in a given frequency range. Then, a detailed model and a spectral analysis of the entire transmission system is developed, deriving how factors such as submarine cable parameters, static reactive compensation, etc… affect to the amplitude and location of the resonances of the system. After that, a solution to mitigate the negative effect of these resonances is proposed, based on a passive filter design procedure. Finally, simulation results validate the performance of the offshore wind park under the proposed approach.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.